Airbags have proved effective in protecting occupants of motor vehicles during accidents. New vehicles usually offer airbags for the driver's side, and sometimes passenger's side, of the vehicle front seat. Such airbags are installed within the vehicle steering wheel or dashboard. The airbag is usually activated by sensors positioned under the vehicle hood near the front of the vehicle. A predetermined impact activates the sensors, which communicate with a computer to direct the airbag inflation. Commonly, the ignition of a small amount of volatile chemical (such as sodium azide) produces gaseous nitrogen to inflate the airbag within about 0.05 seconds after an impact. Such airbags are typically made of opaque, carbon-reinforced plastic and deflate within a few hundredths of a second after inflation.
While such airbag systems usually provide excellent protection, disadvantages exist. The complicated electronics associated with airbags are vulnerable to malfunction, especially if exposed to heat, vibration, and corrosive elements under the hood of the vehicle. Moreover, airbags inflating from the steering wheel or dashboard are capable of injuring an occupant if the occupant is bent forward prior to airbag inflation. Such airbags may also project loose items at the occupant.
For cars not factory equipped with airbags, retrofit airbag systems have been developed. Such retrofit systems generally include airbags that inflate downward from the vehicle ceiling or upward from the occupant lap belt. A ceiling-based airbag may strike an occupant in the back of the head if the occupant is bent forward prior to the airbag inflation.
Moreover, such airbags are not entirely satisfactory in that they may rely on malfunction-prone electronic or magnetic systems for airbag inflation. Such retrofit inflation systems also tend to react relatively slowly, and inflate relatively small airbags that provide limited protection.